Thousands of homeowners are about to get slammed with higher monthly payments

Last year, when Jennifer Hernandez received notice that the mortgage payments on her Houston home would jump about $2,000 per month, she was stunned.

Hernandez refinanced her home loan in 2016 using an adjustable-rate mortgage loan, which has a low introductory rate for a fixed initial period.

Unlike the more popular fixed-rate mortgage loans, ARMs can offer temporary relief for homebuyers who want to avoid paying higher mortgage rates — however, they also come with risk. After the fixed introductory period ­— usually five, seven or ten years ­— the rate...